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Assess Simulation and Compare Output Data

Overview

Functional testing requires assessing simulation behavior and comparing simulation output to expected output. For example, you can:

  • Analyze signal behavior in a time interval after an event.

  • Compare two variables during simulation.

  • Compare timeseries data to a baseline.

  • Find peaks in timeseries data, and compare the peaks to a pattern.

This topic provides an overview to help you author assessments for your particular application. In the topic, you can find links to more detailed examples of each assessment.

You can include assessments in a test case, a model, or a test harness.

  • In a test case, you can:

    • Compare simulation output to baseline data.

    • Compare the output of two simulations.

    • Post-process simulation output using a custom script.

    • Assess temporal properties using logical and temporal assessments.

  • In a test harness or model, you can:

    • Verify logical conditions in run-time using a verify statement, which returns a pass, fail, or untested result for each time step.

    • Use assert statements to stop simulation on a failure.

    • Use blocks from the Model Verification or Simulink® Design Verifier™ library.

Compare Simulation Data to Baseline Data or Another Simulation

Baseline criteria are tolerances for simulation data compared to baseline data. Equivalence criteria are tolerances for two sets of simulation data, each from a different simulation. You can set tolerances for numeric, enumerated, or logical data.

Set a numeric tolerance using absolute or relative tolerances. Set time tolerances using leading and lagging tolerances. For numeric data, you can specify absolute tolerance, relative tolerance, leading tolerance, or lagging tolerance. For enumerated or logical data, you can specify leading or lagging tolerance. Results outside the tolerances fail. For more information, see Set Signal Tolerances.

Specify the baseline data and tolerances in the Test Manager Baseline Criteria or Equivalence Criteria section. Results appear in the Results and Artifacts pane. The comparison plot displays the data and differences.

This graphic shows an example of baseline criteria. The baseline criteria sets a relative tolerance for signals output torque and vehicle speed.

Post-Process Results With a Custom Script

You can analyze simulation data using specialized functions by using a custom criteria script. For example, you could find peaks in timeseries data using Curve Fitting Toolbox™ functions. A custom criteria script is MATLAB® code that runs after the simulation. Custom criteria scripts use the MATLAB Unit Test framework.

Write a custom criteria script in the Test Manager Custom Criteria section of the test case. Custom criteria results appear in the Results and Artifacts pane. Results are shown for individual MATLAB Unit Test qualifications. For more information, see Process Test Results with Custom Scripts.

This simple test case custom criteria verifies that the value of slope is greater than 0.

% A simple custom criteria
test.verifyGreaterThan(slope,0,'slope must be greater than 0')

Run-Time Assessments

verify Statements

For general run-time assessments, use verify statements. A verify statement evaluates a logical expression and returns a pass, fail, or untested result for each simulation time step. verify statements can include temporal and conditional syntax. A failure does not stop simulation.

Enter verify statements in a Test Assessment or Test Sequence block, using the Test Sequence Editor. You can use verify statements with or without a test case in the Test Manager. Without a test case, results appear in the Simulation Data Inspector. With a test case, results appear in the Test Manager.

For information on using verify statements in your model, see Assess Model Simulation Using verify Statements.

assert Statements

You can use assert statements in a Test Assessment or Test Sequence block to stop executing an invalid test. assert evaluates a logical argument, but unlike verify, assert stops simulation. Failures appear as simulation errors. To make results easier to interpret, add an optional message.

For example, if a component under test outputs two signals h and k, and the test requires h and k to initialize to 0, use assert to stop the test if the signals do not initialize. This assert statement returns a message 'Signals must initialize to 0' if the logical condition h == 0 && k == 0 fails.

Assessments for Real-Time Testing

If you are using a real-time test case, or if you want to reuse a desktop simulation test case on a real-time target, use verify statements. verify statements are built into the real-time application, and run on the real-time target. See Assess Model Simulation Using verify Statements.

Model Verification Blocks

Use blocks from the Simulink Model Verification library or the Simulink Design Verifier library to assess signals in your model or test harness. pass, fail, or untested results from each block appear in the Test Manager. For more information, see Examine Model Verification Results by Using Simulation Data Inspector.

Note

All Model Verification library blocks, including the Assertion block, do not produce verification results when used in For Each subsystems. Use a Test Sequence block with verify statements instead.

Examples of Run-Time Assessments

This example test harness includes:

  • A verify statement in the Test Assessment block, verifying that signalC >= 5.

  • An Assertion block verifying that throttle >= 0.

Logical and Temporal Assessments

Logical and temporal assessments evaluate temporal properties such as model timing and event ordering over logged data. Use temporal assessments for additional system verification after the simulation is complete. Temporal assessments are associated with test cases in the Test Manager. Author temporal assessments by using the Logical and Temporal Assessments Editor. See Assess Temporal Logic by Using Temporal Assessments for more information.

Temporal assessment evaluation results appear in the Results and Artifacts pane. Use the Expression Tree to investigate results in detail. If you have a Simulink Requirements™ license, you can establish traceability between requirements and temporal assessments by creating requirement links. See Link to Requirements for more information.

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